A total of 450 out of 5000 chicks of two-old with a history of respiratory symptoms followed by death 1 to 4 days from onset of signs. From which sixteen of freshly dead chicks were examined at postmortem and mycologically. In addition, experimental infection with isolated Aspergillus fumigatus from naturally infected chicks via contaminated litter were carried out. The clinical findings were recorded including respiratory signs, droopiness, anorexia , watery diarrhea of  offensive odour and lack of equilibrium. Also, 0, one, seven, one, two, four and six chicks died on 1, 2, 3, 4, 5, 6, and 7 days post infection respectively. Post mortem examination of freshly dead experimentally infected chicks revealed pneumonia , white yellowish caseous nodules on the lungs and air sac. Mycologically, the cases were diagnosed as infection with Aspergillus fumigatus.